Some Data Warehouse's provide what is known as a Common Alerting Mechanism (CAM). CAM provides an alerting service wherein clients, send requests for action sets to be performed. An action set is a named aggregation of one or more physical actions, where a physical action may be one of: send email; generate SNMP trap; run a user-defined program; etc.
The CAM service receives alert requests, executes the actions configured for the alert, and logs the statuses of the actions to database tables. For each action set, statuses are logged at two levels:                1) A summary status is written in table cam_alert_log; one status per action set.        2) Each individual, physical, action within the action set is assigned its own status in table cam_alert_status_log; e.g. an action set that sends an email and generates a Simple Network Management Protocol (SNMP) trap will have two statuses in cam_alert_status_log: one for the email and one for the trap.        
An action set's summary status reflects the set of statuses for its physical actions, and will change dynamically as its associated physical actions are executed, encounter errors, or complete successfully. For example, a typical action set will begin with a PENDING status, meaning that the associated physical actions have not yet completed. If all physical actions complete successfully, then the action set summary status is updated to SUCCESS. On the other hand, if all physical actions fail, then the summary status is updated to FAILED. Finally, if some physical actions were successful and others failed, then the summary status is updated to PARTIAL.
CAM has the capability to process multiple alert actions at any given time. Monitoring the statuses of the physical actions and rolling them up to the corresponding action set summary statuses in cam_alert_log are costly operations for the CAM service.